upgrading pollinate causes conffile prompt

[Martin Pitt]

Today, upgrading our autopkgtest machines hangs eternally on

Unpacking pollinate (3.17-0ubuntu1) over (3.12-0ubuntu1) ...
[...]
Setting up pollinate (3.17-0ubuntu1) ...

Configuration file '/etc/init/pollinate.conf'
 ==> Modified (by you or by a script) since installation.
 ==> Package distributor has shipped an updated version.
   What would you like to do about it ? Your options are:
    Y or I : install the package maintainer's version
    N or O : keep your currently-installed version
      D : show the differences between the versions
      Z : start a shell to examine the situation
 The default action is to keep your current version.

There certainly has not been any manual modification to this file. It shouldn't ask a conffile prompt for an unmodified file. If that changed from config file to dpkg conffile, it should keep around an md5sum list of "unmodified" files from previous versions, and silently update the file to the current version for all of them.